'Other' option for Email service provider missing when creating new email channel

Problem

When a JSM Server license is applied, the 'Other' option for Email service provider is missing when creating new email channel for a Service project. Only Google, Microsoft and Yahoo options are available

The 'Other' option is available when Data Center license is applied.

Environment

JSM 4.22.0

Steps to Reproduce

1. Create Service project
2. Navigate to (Project > Project settings > Email requests)
3. Click on 'Create Channel' button
4. Click on the dropdown for Email service provider

Expected Results

1. Four options are available: Google, Microsoft, Yahoo, Others
   

Actual Results

1. Three options are available: Google, Microsoft, Yahoo
   

Workaround

This is a Bug in the multiple email channels feature screen. There is a dark feature available that can disable the multiple email channels feature which will allow the 'Other' option to be displayed:

1. To access dark features page, follow the instructions here: https://confluence.atlassian.com/jirakb/enable-dark-feature-in-jira-959286331.html
2. Once there, add this property:

   sd.multi.incoming.email.support.disabled

   Note that this will disable the multiple email channels feature in the entire environment, affecting all projects